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11/27/05 FCST: Southern Plains

Making it short for now... A synoptic trough will continue to amplify as it pushes into the Mississippi Valley on MON with rich boundary layer moisture forecasted to advect northward in response to a 40kt SW LLJ spread across the warm sector... This will result a favorable setup for severe thunderstorms, including the potential for AT LEAST a widespread damaging wind event. Overall, the threat should extend from eastern TX and then points north-northeast, possibley all the way into TN and KY.

Strong +40kt SW LLJ --> http://www.rap.ucar.edu/weather/model/disp...hr132hr144hr156

And the resultant moisture advection --> http://www.rap.ucar.edu/weather/model/disp...hr132hr144hr156
This has potential to be a significant severe weather event for East Texas/Louisiana & Arklatex on Sunday. Too early for any specifics. Let's just say I'm a little upset my flight from Nashville (for Thanskgiving) doesn't land in Houston 'till 4pm Sunday...
I've been watching GFS model maps regarding the upcoming setup since Sunday and last night, it shows a rather potent low w/ neutral trough moving ENE from SRn New Mexico to SE Kansas / NE Oklahoma by 0Z Monday. After the potent low and trough move out, another big trough will dig in the western third of the US and usher in some rather cold air.
The 500mb vort maps ( 0Z Monday) over at COD show the low as being rather potent.

Right now, the low is sitting west of California out in the ocean waiting to move east. It looks pretty good on visible and water vapor satellite.

Whether or not all this pans out remains to be seen. But it appears that the weather for next week looks to be unsettled for the US. Particularily the Northern 2/3rds (including the mid-south).
Whoa buddy, do I like what I see. This is a setup that really favors significant severe over my area. The 18z model run has pushed the main upper level energy a bit further north and I don't really buy that. The SFC low also runs up towards IL from OK.....simply nuts with the pattern we are in. I don't see the trough wrapping up that fast.

I had my doubts about the atmosphere charging back up, but with the LLJ kicking above 60-65kts by 12z MON across western portions of the BMX CWA. All in all, it looks like a big outbreak across the Mid-south with damaging winds, large hail and possibly strong tornadoes in store.

Another chaser fest to come. :twisted:
Well, the event is still nearly 102hrs out, but will make a more detailed forecast... After a review of the 12z GFS there sdoes appear to be potential for a widespread damaging wind event, along with the potential for a few tornadoes, especially with any discrete cells that form along the dryline. Based on the GFS forecast, low-level cyclogenesis will be underway during the start of the period, with a 40-50kt SW LLJ likely advecting in the progged surface Tds into the low 60s across the southern half of the warm sector. In general, the 80-125kt SW upper flow atop backed / nearly backed boundary layer flow south and east of the low creates a very favorable shear environment for fast-moving, strong supercells. The strong low-level wind fields and a favorabley saturated low-level airmass will help create a well-mixed boundary layer, particularly across eastern TX, into LA and AR and then possibley stretching into TN and MS during the late afternoon. Overall, this pretty much looks like a SLIGHTLY less significant version of last Tuesday, and from the looks of it now -- I would have to bet on widespread damaging winds and at least a few tornadoes (with a more concentrated threat area along the dryline across the southern half of the warm sector, with another threat area extending all the way into the OH valley, again, near the warm front).
Nice to see that our second season is gearing up. Am watching and waiting to see if this manifests into one heck of a day for my area. I may give up my seat at Reliant and go 'nader hunting. :lol:

Will be watching and comaparing everyone's input, especially on Saturday.
Still a few days out...but the models have been fairly steady during the past few runs.... so with "some" confidence I offer....

If I had the day off...i would be tempted to make a run up i-35 and play the potential for a low-topped supercell event near the kansas turnpike northeast of wichita. Classic upper system/surface cyclone will produce very nice low and deep layer shear profiles....and the latest nam creates a bullseye of 3 km cape just east of the surface low as it wraps 55F sfc dews back into eastern kansas. I don't think a 'nader or two would be out of the question.

.....of course now, the 12z nam is quicker with the system pushing the threat more toward the mo/ks border....but also has the surface wave more stretched out nne/ssw with not as much turning in the lower levels.
This could be a repeat of Nov. 12, but this time over southern Iowa/Northern Missouri. The shear will be amazing, the cap will be strong, and there will be strong dynamics in place. 850mb moisture is going to be a problem, but it doesn't appear like surface moisture will be as much of a problem.

Like the Nov. 12th setup, this is very conditional on everything coming together just right. But once again this could be a significant severe weather event with tornadoes.
Luckily I'm in St. Louis for the weekend visiting a friend. I don't think it'll hurt to chase on my way back to Wisconsin.

Latest NAM gives me decent confidence for Central and Northern parts of Missouri into S. IA. Surface moisture well juxtaposed with upper flow at very least leads me to believe dynamic forcing will be strong enough for some severe convecting. Obviously strong surface based convection is conditional based on moisture depth/diurnal heating. After chasing Nov. 12 and the horrendous day it was, I'm a little pessimistic about Sunday. However, being in St. Louis right now I make take my chances.
I think tornadoes are a decent possibility on Sunday, but there are also some serious problems with this setup IMO. My biggest concerns right now are storm motion(40-50kts), terrain(poor road networks, hills, and trees), and cloud cover/instability(lapse rates aren't very steep according to the 0Z NAM). Great dynamics can't trump all of those problems, but it will definitely keep me watching. I'll just have to wait and see what it looks like tomorrow.
After looking over the models, there is still some pretty good potential for this system. A strengthening SW LLJ will allow for rapid deep moisture transport toward the Mississippi valley beginning tomorrow, and continue through the day on Sunday. Surface cyclogenesis will be underway during the start of the period, with the surface low near the TX/OK panhandles forecasted to deepen as it pushes eastward toward the Mississippi valley by Sunday morning. Relatively moist and backed boundary layer flow beneath SW 60-80kt mid-level flow yields favorable deep-layer vertical shear profiles for supercell structures, with NAM bringing in 200-400m2/s2 0-1km SRH across the warm sector, given the backed surface flow pattern, which will increase the potential for tornadoes with any surface-based storms. I think the area east of the dryline will see adequate convergance by early afternoon to initiate deep convection, and any sustained surface-based storm should be able to take on a supercellular structure, given strongly sheared and at least marginally buoyant boundary layer airmass -- I would have to agree with Scott's target area of central MO, which is where I would play.
Michael has a good point on storm motion in this situation. Good luck catching these things with the increasing wind profiles. I also think Nick is onto something ahead of the dryline and further east along the warm frontal boundary. Given the steepe height falls progged and strengthening SFC low, the gradient that forms along the squall line will also favor tornadoes considering it will allow small scale backing at the SFC given the gradient just ahead of the line.
Well the 12z NAM is definitely an improvement over the 00Z NAM, having flopped back to a far less progressive/less strung out solution. Not sure if the GFS has improved since 00z as I didn't see it, but the 12Z GFS looks similar to the 12z NAM. NAM/NAM-KF model soundings northeast of Kansas City remind me strongly of the Nov 12 event, with the models forecasting a significant 850-750mb cap to break explosively around 21Z as strong upper difluence and pva start to affect the area. If insolation isn't as strong or moisture is more shallow than the models suggest, than cap breakage may take longer as other posters have mentioned. Also agree w/ the storm speed being aproblem, particularly on the not-nice roads of northern MO. Degree of insolation and the ultimate convective mode look to be the big question marks to me right now.
Well, things still look on track to me with the latest 12 runs... Strong forcing and backed boundary layer flow ahead of amplified mid-level impulse will weaken the inversion by mid-afternoon. Deep shear profiles favors a few isolated supercells forming ahead of the dryline by mid-afternoon, with the approach of shortwave around 21z, with marginal surface-based instability and strong deep/low-level shear favoring the potential for tornadoes. The storms should consolidate into a squall line with embedded supercell structures over eastern MO by the late evening, with a continued threat for tornadoes and damaging winds. Very favorable low-level wind fields has poised forecasted 200-400m2/s2 0-1km SRH across MO / IL by mid-day tomorrow. At this time, I would have to say damaging winds and at least a few tornadoes remain a decent threat for MO / IL through the afternoon and evening.
After looking at more forecast soundings further to the west, it makes me think of northwest MO as a good target area. Unmodified EAX sounding at 21z SUN shows a well-mixed boundary layer, with dry adiabatic lapse rates present through the sfc-1.5km layer and strong veering flow. Steep low-level lapse rates and moist surface inflow yields 1391j/kg of sbCAPE, per this NAM forecast sounding, with no inversion left by 21z.
Anyone perusing the latest NAM guidance will note things look a might bit breezier and even more wrapped up. I have no problems with this if it pans out... but accordingly, forecast uvm fields are far stronger than before and suggest that forcing for ascent with this system will *not* exactly be subtle... lol. Of course, the devil will be in the details... boundary layer destabilization, convective mode, forward speed of the occluded front etc. I have to work until 2pm but am still thinking I'd prefer to play the northeast quadrant of the developing closed low anyway, where synoptic lift might be comparatively weaker and where the dryline/cold front/occluded front thing isn't mixing eastward at 9999mph. I'll be watching things closely in the morning. If nothing else it sure is an exciting system close to home!
Chase target for November 27

Chase target:
Miami, OK (along I-44 in the extreme NERN corner of the state)

Storm initiation around noon.

Storm type and evolution:
All types of severe WX will be possible, including a small tornado threat. Storm motion will be very rapid, with cells traveling to the NE at 60 mph.

An active fall storm system will affect much of the central US with a full spectrum of hazardous WX including severe storms and heavy snow over the next 48 hours. Active WX setup upstairs at 00Z, with 180kt H3 max over NRN CA diving SE towards base of negatively-tilted trough. Several embedded waves were noted, with lead S/WV lifting through ERN NM/WRN TX along with primary wave in exit region of streak now moving through AZ. At the SFC, slow cyclogenesis has commenced in WRN KS. This low begin to rapidly deepen beginning this time tomorrow when the best upper support arrives, and it will take a track through NWRN IA into MN through the day Monday as heavy snow develops to the N and W of this track.

SFC WF extends E from the low along the NE/KS border and IA/MO border. A 60kt LLJ is developing and nosing into WRN IA. Significant moisture and instability, rooted just above the BL, is being advected towards the upper-Midwest. 00Z TOP and OAX soundings both show 100-150mb deep moist layer along with region of steep lapse rates just above a stable layer. Later this evening, H85 WF should bisect IA from NW to SE. Convergence along front, and isentropic lift of around –5ub/S on 290K through 296K surfaces to the N of the front may provide the focus for some elevated showers and storms in NRN IA and SRN MN. No severe WX is expected.

The SFC low will rapidly deepen and lift from NWRN OK into KS. A secondary developing WF along the OK and KS border will provide the focus for severe WX early in the afternoon, while a dryline dives to the E towards the target by mid-afternoon. The resulting triple point will lift rapidly off to the NE with the advance of the DL. As is often the case this late in the season, moderate instability will be coupled with very strong mid- and upper-level forcing and shear. Mid-afternoon MLCAPE’s will generally be below 1000J/kG while deep layer shear to 70 kts in left-exit region of H5 streak will result in very long but only slightly curved hodographs which will support organized severe WX with the primary threat severe wind gusts to 80 mph.

Sunday night and Monday:
Attention will turn from severe convective WX to the first significant snowstorm of the season. Main axis of heavy snow will occur along an axis of deformation to the N and W of the SFC low track in SD/ND/MN.

- bill
SPC's latest day 2 outlook states that there may be embedded supercells within the squall line as it marches east tomorrow PM. Right now, they have just a slight risk out but I think a moderate risk, provided that all this gels together at the right time, is in order. They also stated that there will be enough directional shear for some discreet cells out ahead of the squall line, particularily over the Ozarks and back toward extreme NE OK.
By the time it reaches my area, it will be dark (egads!!) so it ought to be interesting for me tomorrow!
Right now, KLZK VWP is showing 15-20 kt SSE surface winds, 40 kt S winds around 3,000 ft and S / SSW winds in varying wind speeds above 5,000 ft, veering toward the right with height. Upper level winds are at 90 kts @ 35kft out of the SSW. Numerous showers are lifting north @ 40 to 45mph.
--> http://www.midwestchase.com/november_sat_outlook14.gif

That surface analysis is for 21z and the outlined threat area is for through all of tomorrow. The approaching mid-level impulse coupling with low-level convergance ahead of the dryline should provide sufficient upward motion to release instability... Highly favorable deep and low-level shear will enhance storm organization and supercell formation is quite likely. With the main threats being both damaging winds and isolated tornadoes.. Unmodified DMO NAM model sounding for 21z SUN shows a well-mixed boundary layer -- owed to strong flow present with nearly dry adiabatic lapse rates. Strong rotation (from +100kt SW flow at 250mb, to backed southeast flow at the sfc) yields widespread >60kt deep-layer shear across the warm sector -- indicating the potential for long-lived updrafts. In addition, >55F sfc Tds yields marginal to moderate sfc-based instability across the warm sector, which when combined with 250-400m2/s2 0-1km SRH indicates the potential for an isolated strong tornado or two. Storms may initially form ahead of the dryline around 21z across western MO... Storms should then evolve into a broken line by evening, with a continued threat for damaging winds and isolated tornadoes well into IL. As of now, I think a target of Sedalia, MO would be a pretty good starting point... Good luck to all tomorrow!
I noticed both ETA and GFS are showing a well defined dry incursion at
700mb at 0Z Mon; just ahead of the progged dryline bulge in SE
Ks at that time. Very classic synoptic set up in many ways. I like that the strongest veering with height is in the lowest 1-2 Km. However, I expect
no storm slower than 40kts and a good deal faster S of MO., with
storm motions almost due N. That actually can help with the road situation. Considering the likely speeds and locations for most of the prospecticve supercell activity, these storms may be unchaseable. Well, at least the jungles have no leaves now:) A small window of opportunity may be there for extreme E. Ks and W Mo by late afternoon. Point, click and get out of the way, may be the best one can do for this round--good luck to anyone who gives it a shot.
Wow. This November has been absolutely relentless in terms of tornado outbreaks and general severe weather, and tha trend looks to continue today.
From the SPC Day 1 1300 UTC Outlook:

The setup is highly conducive for a few potentially strong, damaging tornadoes, especially across far east KS/southwestern MO/northern AR/far northeastern OK with initial discrete supercells that form on the triple point, which should develop here around mid-afternoon. :shock: The shear this system has to work with is insane for this time of year and will overcome the issue of SBCAPE's of less than 1000 with no problem. I think I'm going to call my aunt; she lives southwest of Jefferson City. I love her dearly, but she pays no attention to the weather. And this is going to be a day, I fear, where paying attention could save lives. Anyone living in an area from Jefferson City, MO, to Poplar Bluff, MO to Little Rock, AR to Tulsa, OK to Overland Park, KS needs to be on high alert this afternoon and evening. Good luck to anyone who tries to chase these storms; they'll be haulin' ass northeast through the Ozark Jungle!
Pretty impressive... the base of the mid/upper trof is starting to translate through west TX, and the Jayton profiler has shown mid-level (6-8km) flow of 110-120kts during the past 3 hrs. This is 15-25kts stronger (!!!) than what the 12z NAM has for a 500mb wind max from 12-15Z. I don't know that this specifically will have much of an impact on the convective evolution later today, but I wouldn't be surprised to see an even deeper surface low develop this aftn-eve than is progged. Just got a look at the new GFS, and it may be accounting for the stronger kinematics as it has a deeper system over the northeast quarter of KS by 00Z (984mb)

Edit, Just saw the 15Z ruc... it has picked up on this, showing "breezier" mid-level flow. It holds the surface low over Salina KS at 00Z and is down to 983mb!
I'm already in my Target area... my house in Pittsburg Kansas. Very impressive setup.
I'm stuck in my target area (my house), of course there would be this nice of a setup only weeks after my chase vehicle throws a rod. Plus I have to find someone to cover for me at work. Anyone need a chase partner in the Bentonville, Arkansas area? If so send me a PM.